ENGLEWOOD, Colo. -- Yes, it's most certainly a passing league. Yes, it's all about the quarterback.

Yes, the Denver Broncos' three Super Bowl wins have come with John Elway and Peyton Manning at quarterback.

But in the wake of their first playoff miss since 2010, much of the Broncos' reconstruction on offense has been about what happens when the team doesn't throw. Because it was their dismal running game that turned their offense into a stagnant affair with quarterbacks who had no way to slow down the pass-rushers.

Even during their recent Super Bowl seasons, running the ball consistently has been a struggle for the Broncos, who haven't had a 1,200-yard rusher since 2004. Jake Roth/USA TODAY Sports

Or as former coach Gary Kubiak said at the Super Bowl: "That's going to be one of my biggest frustrations about all of it looking back. That we worked and worked and we never could get it the way we wanted it."

The league is decidedly a chuck-it-around affair these days -- 13 quarterbacks topped 4,000 yards passing last season -- and defenses have reacted. The NFL has made it more difficult to cover receivers with contact rules, so for many defensive coordinators the only recourse has been rushing the quarterback.

On offense, line play -- either because of the turnover caused by free agency or the erosion of NFL-style fundamentals -- is not always what it needs to be. But a team that can run the ball can protect its quarterback better. It is worth noting the teams in the Super Bowl ranked No. 5 and No. 7 in the NFL in rushing, even though the Falcons have quarterback Matt Ryan, who won the league’s MVP award, and the Patriots have Tom Brady, who added to his Hall of Fame resume with another Super Bowl win.

"There's always room to run the ball in your offense, and it helps your quarterback be his best," said former Broncos running backs coach Bobby Turner, who was on the Falcons' staff last season. "In Denver we had T.D. [Terrell Davis] and John [Elway], they went together."

Elway is the Broncos' top football decision-maker these days, and his new coach Vance Joseph wants the Broncos to carve out something more than ornamental yardage in the running game. It's why their checkbook opened in free agency for a guard (Ronald Leary) and a tackle (Menelik Watson).

"You watch Leary play, he played the game with an attitude, he was physical, he was trying to finish blocks," Joseph said. "It’s the same with Watson. Both of those kids play with an attitude. That is something that helps the entire culture of your offensive line. Running the ball on our terms, heavy box or light box, let’s run the football. That is the attitude that you want."

It has been the theme of the Broncos' offseason. But this isn’t new.

The Broncos enjoyed prosperity on offense in Manning’s four seasons -- four division titles, two Super Bowl trips and the league’s first 600-point season in 2013. But even the guy who called the plays in two of those years --Miami Dolphins coach Adam Gase -- often expressed frustration about the running game.

The Broncos haven't had a 1,000-yard rusher since 2013 (Knowshon Moreno) and haven't had a 1,200-yard rusher since Reuben Droughns in 2004. Though they definitely like their prospects at quarterback (Trevor Siemian and Paxton Lynch), the bottom line is the Broncos won’t know what either can be until they have protection.

That’s why folks have heard Elway and Joseph repeatedly use words such as "mentality" and "attitude" when talking about what they want to see more of from the offense this fall. The Broncos are a team of defensive swagger and want to see a little more of that from the guys on the other side of the ball.

"I definitely take more enjoyment blocking for the run," Leary said. "I feel like run blocking is all about attitude. It’s big guy on big guy ... Once you see one guy doing it, then OK, that looks fun knocking people around. Then the next guy does it and it just trickles down. That is how you become a dominant offensive line."

The Broncos have plenty of work to do. They still have an opening at left tackle, and they could use a running back in the mix who has some big-play pop.

But their intentions have been clear in the offseason to this point.

"I grew up fighting my whole life," Watson said. "It’s nothing new to get physical. It’s what I like to do. It's why I'm an offensive lineman. It's just part of the game. It's a physical game. You can't go into this thing timid. You've got to be the aggressor. That's what I like to be."